I have a Carrier model 396JAW 036045, about 23 years old. The pilot ignites, the main burners come on for a short while, then the fan comes on and the heater acts normally. But after a few minutes the main burners shut off, with some solenoid chatter preceding the shut off. The pilot then stays lit but not the main burners. I have replaced the limit switch already.

I suspect the problem is the pilot burner/warp switch. Can anyone share with me a way to temporarily bypass the warp switch to determine if that is the problem, or to otherwise troubleshoot it? It has the Carrier Bryant Furnace 3 Wire Pilot Burner LH680005 type of module, with the yellow, green and white wires.

I have no intention of permanently bypassing something so important as the heat sensor, so don't worry about that. This is for testing purposes only.

Also, can the warp switch be cleaned or replaced without replacing the pilot too? Money is a serious concern.

Solinoid chatter could be a safety switch (pressure switch/roll out/limit or the pilot safety) , the connections to those switches or the valve solinoid itself. The warp switch is a logical possibility but you will need to meter those warp switch lines while its running OK to see what changes when the lockout occurs. I don't think it will have an led diagnostic indicator.Because of it's age, remember to observe the pilot flame for a flame change after the main burner starts up or just before the lockout occurs from a possible heat exchanger problem.Let us know what you find as I just saw such a furnace the other day and it looked like a frankenstein mix of early electronic boards in the blower compartment, beside to the gas valve and another almost behind the inducer assy.

To the - it is a warp switch; these don't use a rollout, so there's no button to push. But thanks anyway.

To anyone else who might have the same - If you wait for the pilot to come on and the main burners to ignite, then jumper the white and yellow wires coming from the pilot valve flame sensor (in this case, the warp switch) you will bypass the warp switch and if the burner then acts normally, you know the switch is bad. But THIS IS ONLY FOR TESTING PURPOSES WHILE YOU ARE DIRECTLY OBSERVING. THE SAFETY MECHANISM THAT PREVENTS UNBURNED GAS FROM POURING OUT OF THE HEATER IN THE EVENT THAT THE BURNERS GO OUT FOR ANY REASON WILL BE DISABLED. DO NOT LEAVE THE JUMPER IN PLACE. GET A NEW PILOT VALVE/WARP SWITCH.

dfyoung10 -> To the - it is a warp switch; these don't use a rollout, so there's no> button to push. But thanks anyway.> > To anyone else who might have the same - If you wait for the pilot to> come on and the main burners to ignite, then jumper the white and yellow> wires coming from the pilot valve flame sensor (in this case, the warp> switch) you will bypass the warp switch and if the burner then acts> normally, you know the switch is bad. But THIS IS ONLY FOR TESTING> PURPOSES WHILE YOU ARE DIRECTLY OBSERVING. THE SAFETY MECHANISM THAT> PREVENTS UNBURNED GAS FROM POURING OUT OF THE HEATER IN THE EVENT THAT THE> BURNERS GO OUT FOR ANY REASON WILL BE DISABLED. DO NOT LEAVE THE JUMPER IN> PLACE. GET A NEW PILOT VALVE/WARP SWITCH.Did it work, did you blow yourself up? Not many people have a piece of crap furnace like you.